JP3512784B2 - Method for manufacturing thin film transistor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor and is particularly applicable to a liquid crystal electro-optical device, a perfect contact type image sensor device and the like.

[0002]

2. Description of the Related Art Conventionally known insulating gate type field effect semiconductor devices are widely used in various fields. This semiconductor device is formed on a silicon substrate and is used as an IC or an LSI by functionally integrating a large number of semiconductor elements.

On the other hand, a similar insulating gate type field effect semiconductor device, but a thin film type insulating gate type field effect semiconductor device (hereinafter referred to as TFT) formed by laminating thin films on an insulating substrate or the like.
Has been positively started to be used in a switching element portion of a pixel of a liquid crystal electro-optical device, a driving circuit portion, a reading circuit portion of a contact image sensor, and the like.

Since this TFT is formed by laminating thin films on the insulating substrate by the vapor phase method as described above, it can be formed at a low production ambient temperature of about 500 ° C., which is inexpensive soda glass and borosilicate. Acid glass or the like can be used as the substrate.

As described above, a transistor can be easily manufactured on a large-area substrate because it can be manufactured on an inexpensive substrate and its maximum size is limited only to the size of an apparatus for forming a thin film by a vapor phase method. It has the advantage that it can be formed, and therefore, it is expected to be used for a liquid crystal electro-optical device having a matrix structure having a large number of pixels and a one-dimensional or two-dimensional image sensor, and it is partially realized.

A typical structure of this conventional TFT is schematically shown in FIG.

In FIG. 2, 1 is an insulating substrate made of glass, 2 is a thin film semiconductor made of an amorphous semiconductor, and 3 is a thin film semiconductor.
Is a source / drain region, 7 is a source / drain electrode, and 8 is a gate electrode.

In general, such a TFT is formed by first forming a semiconductor film on a substrate and then patterning the semiconductor region 2 in an island shape in a necessary portion using a first mask. Next, the gate insulating film 6 is formed, a gate electrode material is formed on the gate insulating film 6, and the gate electrode 8 and the gate insulating film 6 are patterned using the second mask.

After that, the source and drain regions 3 are formed in the semiconductor region 2 as self-alignment using the photoresist mask formed by the third mask and the gate electrode 8 as a mask.
To form. After that, the interlayer insulating film 4 is formed. Contact holes are formed in the interlayer insulating film for connecting electrodes to the source / drain regions 3 using a fourth mask. After that, after the electrode material is formed, the electrode material is patterned by the fifth mask to form the electrode 7 to complete the TFT.

[0010]

As described above, a general TFT requires five masks, and a complementary TFT requires six masks. Naturally, when forming a complicated integrated circuit, more masks than this number are required. Using a large number of masks in this way requires complicated steps in the process of manufacturing a TFT element, and the number of mask alignments naturally increases. They are,
This causes a decrease in yield and productivity in manufacturing TFT elements. Furthermore, the size of electronic devices using TFT elements, the miniaturization of TFT elements themselves, and the miniaturization of patterns have been factors that further reduce these. Therefore TFT
In the fabrication process, a new T that reduces the number of masks required for TFT fabrication, a process that does not require complicated steps
The structure of FT was desired.

Therefore, the present invention relates to a novel structure and a simple manufacturing process of an insulating gate type field effect semiconductor device, which requires a smaller number of masks than the conventional one.
The feature is that T can be produced.

[0012]

The TFT of the present invention is provided with an anodic oxide film of the material forming the gate electrode near the side surface of the gate electrode, and the electrodes connected to the source and drain regions are the source and drain regions. The electrode that is in contact with the upper surface and the side surface and is connected to the source and the drain extends over the insulating film provided near the side surface of the gate electrode.

That is, as shown in the schematic sectional view of the TFT of the present invention shown in FIG. 1, an anodic oxide film 10 is provided at least near the side surface of the gate electrode 8, and the source is formed from the end face of the anodic oxide film. The upper surface and the side surface of the drain region 3 are slightly protruding, and the electrode 7 is connected to the source / drain region 3 at this protruding portion, and the connection area is large. Further, the electrode 7 extends up to above the insulating film 11 on the gate electrode 8 and is patterned at this portion to be separated into individual electrodes.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A process for manufacturing a TFT having a structure as shown in FIG. 1 is schematically shown in FIGS. In the drawings described in the present specification, the schematic dimensions are shown for the sake of explanation, and the actual dimensions and shapes are slightly different.
Hereinafter, an example of the manufacturing process of the TFT of the present invention will be described with reference to FIGS.

First, as shown in FIG. 3A, a glass substrate,
For example, the semiconductor layer 2 is formed on the crystallized glass 1 having heat resistance. As this semiconductor layer, an amorphous semiconductor,
A wide variety of semiconductors such as polycrystalline semiconductors can be used. As a forming method, a plasma CVD method, a sputtering method, a thermal CVD method, or the like can be selected depending on the kind of semiconductor to be used. Here, the following steps will be described using a polycrystalline silicon semiconductor as an example.

Next, a silicon oxide film 6 to be a gate insulating film is formed on this semiconductor layer 2. Further, on this, aluminum is formed as an electrode material to be a gate electrode, here, as an electrode material. Further, a silicon oxide film is formed as an insulating film 11 on this upper surface by a sputtering method. After this,
The insulating film 11 and the gate electrode 8 are patterned using the first mask. Then, the vicinity of the side surface of the gate electrode 8 is anodized in an electrolytic solution for anodic oxidation, so that at least the non-porous aluminum oxide 10 is
Figure 3 (B) near the side surface of the gate electrode near the channel region.
To form.

As the solution used for this anodic oxidation, typically, a strong acid solution such as sulfuric acid, nitric acid, phosphoric acid or the like, tartaric acid, a mixed acid obtained by mixing citric acid with ethylene glycol, propylene glycol or the like can be used. Also, if necessary,
It is also possible to mix a salt or alkaline solution in order to adjust the pH of this solution.

First, with respect to 1% of a 3% tartaric acid aqueous solution, 9
This substrate was dipped in an AGW electrolytic solution containing propylene glycol at a ratio of 1., an aluminum gate electrode was connected to an anode of a power source, and platinum was used as a cathode to apply a DC power.

The conditions of the anodic oxidation are as follows: a current density of ^2.5 mA / cm ² is applied for 30 minutes in a constant current mode, and then a constant voltage mode is applied for 5 minutes, and aluminum oxide having a thickness of 2500 Å is used as a gate electrode. It was formed near the side surface. When the insulating property of this aluminum oxide was examined using a sample produced under the same conditions as this oxidation treatment, the specific resistance was 10 ⁹ Ωm,
The withstand voltage was an aluminum oxide film having a characteristic of 2 × 10 ⁵ V / cm.

When the surface of this sample was observed with a scanning electron microscope, the surface was magnified up to about 8000 times and irregularities on the surface could be observed, but fine holes could not be observed, and a good insulating coating was obtained. Met.

Next, a silicon oxide film 12 is formed on this upper surface by a plasma CVD method, and from this state, an anisotropic etching process is carried out in a direction substantially perpendicular to the substrate, as shown in FIG.
As shown in (D), silicon oxide 13 is formed on the side wall of the convex portion formed of the insulating film 11, the gate electrode 8 and the anodic oxide film 10.
Leave.

The silicon oxide film 12 is formed at an ambient temperature of 200 ° C., which is lower than usual, during its production so that the etching rate is higher than that of the insulating film 11. Further, as this film, not only a silicon oxide film, but also an organic resin film or another film can be used.

Next, with the remaining silicon oxide 13 and the convex insulating film 11, the gate electrode 8 and the anodic oxide film 10 as a mask, the semiconductor layer 2 thereunder is etched and removed by self-alignment. The state at this time is shown in FIG.

The state of the upper surface at this time is shown in FIG. Further, a cross section corresponding to AA ′ in FIG. 5 is shown in FIG.
Is shown in.

Next, from this state, the silicon oxide film 13 and the gate insulating film 6 are selectively etched away using only the silicon oxide by using the convex portion as a mask, and the semiconductor layer is formed as shown in FIGS. 4 (F) and 5 (B). Part of 2 is exposed from the end of the gate electrode.

Next, the exposed portion is doped with impurities so as to form the source and drain regions. As shown in FIG. 4B, the gate anodic oxide film 10 is formed.
Is used as a mask, and phosphorus ions are ion-implanted from the upper surface of the substrate. In this way, the source / drain region 3 is formed. After that, for activation of the region, laser is irradiated to this portion, and the source and drain regions are activated by laser annealing. In addition to this, a thermal annealing process or the like can be adopted as the activation process.

Next, aluminum to be source and drain electrodes is formed on the upper surface, and the source and drain electrodes are etched into a predetermined pattern by using a second mask to divide the source and drain electrodes. . This state is shown in FIG. Finally, by using the source and drain electrodes 7 and the convex portions as a mask, the semiconductor layer 2 that surrounds the periphery is removed by etching, and the semiconductor layer 2 shown in FIGS.
A TFT as shown in (B) is completed.

In the above description, the manufacturing process of the TFT described above is an example, and it is not limited to the manufacturing process shown in this description. For example, the doping process of impurities in the source and drain regions is performed as described above. In the description, as shown in FIG. 4B, it is performed after the patterning of the semiconductor layer 2. However, in the state of FIG. 3B, the insulating film 11 on the gate is formed.
It is also possible to perform the ion implantation process using the as a mask.

As an example of another method for manufacturing the TFT shown in FIG. 1, FIG. 7 shows a schematic view of the manufacturing process thereof. 3 and 4 in the manufacturing process of the TFT shown in this figure.
The anisotropic etching technique, which is adopted in the manufacturing process of 1., is not used, and the process is configured by a general process technique.

As in the case of FIG. 3, a silicon semiconductor film is formed on the entire surface of the insulating substrate 1 and then the first semiconductor film is formed into an island shape so as to include the source / drain region and the channel forming region of the TFT element. The mask is used to perform patterning to form a portion of the semiconductor film 2 corresponding to the TFT element. A top view at this time is shown in FIG. 9A, and a cross-sectional view in the vicinity of the source, drain, and gate of this TFT region is shown in FIG.
It shows in (A).

Next, a gate insulating film 6, aluminum 8 as a gate electrode material, and an insulating film 11 are formed over the upper surface as shown in FIG. 7B.

Next, using the second mask, these films are etched so as to form a gate portion at a predetermined position of the semiconductor film 2, and a convex portion is completed as shown in FIG. 7C. Then, the semiconductor film 2 is exposed from the convex portion. The state of the upper surface at this time is shown in FIG.

In this state, the anodic oxide film 10 is formed near the side surface of the gate electrode 8 as in the step of FIG. 3B to obtain the state of FIG. 7C. Next, the exposed semiconductor film 2 is doped with impurity ions for the source and drain to form the source and drain regions 3 as shown in FIG.

This ion doping is performed by performing a process such as obliquely implanting ions or performing a diffusion process of impurities so that the boundary between the source or drain and the channel region semiconductor is near the end of the gate electrode 8, that is, The anodic oxide film 10 should be on the inner side of the edge. As a result, even if the source and drain electrodes are provided in the vicinity of the contact between the anodic oxide film 10 and the gate insulating film 6, no short circuit occurs, and the anodic oxide film 10 alone can ensure sufficient insulation. it can.

Next, a metal film is formed over these entire surfaces, and then a third mask is used to extend this electrode onto the insulating film 11 to divide the source / drain electrode 7. , A structure as shown in FIG. 8 (B) is obtained. Next, in order to remove the semiconductor film protruding from the source / drain electrodes 7, an etching process is performed using the source / drain electrodes 7 as a mask to obtain the state of FIG. 10A to complete the TFT of the present invention. .

Compared to the manufacturing method shown in FIG. 3, in the step after the semiconductor layer 2 is formed and before the gate electrode is formed, a new photomask is used and the semiconductor layer is patterned into an island shape only in the vicinity of the TFT region. As shown in FIGS. 9 and 10, the semiconductor layer 2 is formed under the lead wiring portion of the gate electrode.
Does not exist and only the substrate or the insulating film on the substrate exists, and it is possible not to configure the gate electrode wiring and the capacitor in this portion. With this configuration, a TFT capable of responding at a higher speed can be manufactured with three masks. This state is shown in B of the top view of FIG.
A cross-sectional view taken along line -B 'is shown in FIG.

Thus, according to the present invention, only a few
It became possible to fabricate a TFT by using one mask. When the TFT has a complementary structure, it can be achieved by adding one or two masks.

The external connection to the gate electrode is performed by forming an anodic oxide film so that a part of the gate electrode does not come into contact with the anodizing electrolyte during the anodizing process, or by forming the last unnecessary semiconductor. After etching the layers, the source and drain electrodes and the anodic oxide film are selectively etched to remove the anodic oxide film exposed to the outside, whereby connection can be established. Of course, it is also possible to newly use another mask and make a contact hole in the insulating film at a specific place to connect the insulating film.

[0039]

[Embodiment 1] This embodiment shows an example in which the TFT of the present invention is applied to an active matrix type liquid crystal electro-optical device having a circuit configuration as shown in FIG.
As is apparent from FIG. 11, the active element of the present embodiment has a complementary structure, and the PT for one pixel electrode is
FT and NTFT are provided.

FIG. 15 shows the actual arrangement of electrodes and the like corresponding to this circuit structure. In order to simplify the description, only the part corresponding to 2 × 2 is shown.

First, a method of manufacturing a substrate for a liquid crystal electro-optical device used in this embodiment will be described with reference to FIGS. In FIG. 12A, a silicon oxide film as a blocking layer 51 is formed by a magnetron RF (radio frequency) sputtering method on a glass 50 such as quartz glass which can withstand a heat treatment at 700 ° C. or less, for example, about 600 ° C., which is not expensive.
It is made to a thickness of 00 to 3000Å. Process conditions are 100% oxygen atmosphere, film forming temperature 15 ° C., output 400 to 80.
The pressure was 0 W and the pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 Å / min.

A silicon film 52, which will later become a source, drain, and channel formation region, is formed on this by LPCVD (Low Pressure Vapor Phase) method, sputtering method or plasma CVD method. When forming by the reduced pressure vapor phase method, it is 1 more than the crystallization temperature.
450-550 ° C, which is low by 00-200 ° C, for example, 530 ° C
CVD of disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ )
The film was supplied to the apparatus to form a film. The reactor pressure is 30-300
It was Pa. The film forming rate was 50 to 250 Å / min.
Threshold voltage (Vt) between PTFT and NTFT
In order to control the concentration to be substantially the same as that of h), boron may be added during the film formation with diborane at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ .

When the sputtering method is used, the back pressure before the sputtering is set to 1 × 10 ^-5 Pa or less, the single crystal silicon is used as the target, and the atmosphere is mixed with 20% to 80% of hydrogen in argon. For example, argon is 20% and hydrogen is 80%.
The film forming temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

When the silicon film is formed by the plasma CVD method, the temperature is, for example, 300 ° C., and monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used. These were introduced into a PCVD apparatus, and high-frequency power of 13.56 MHz was applied to form a film.

The film formed by these methods is
5 × 10 oxygen^{twenty one}cm^-3The following is preferable. This acid
When the elemental concentration is high, it is difficult to crystallize and the thermal annealing temperature is
Higher or longer thermal anneal times must be provided.
If it is too small, the backlight will turn off the light.
The current will increase. Therefore 4 × 10¹⁹~ 4 x 10 ^{twenty one}
cm^-3And the range. 4 × 10 for hydrogen²⁰cm^-3And silicon 4
× 10^{twenty two}cm^-3Was 1 atom%. Also,
To promote crystallization of the source and drain
Therefore, the oxygen concentration is 7 × 10¹⁹cm^-3Below, preferably 1 × 10¹⁹
cm^-3The following is to form the channel of the TFT that makes up the pixel
5 × 10 oxygen only in the region by ion implantation²⁰~ 5 x 10
^{twenty one}cm^-3You may add so that it may become. Then the peripheral circuit
This TFT does not emit light because it does not emit light.
With less carrier and higher carrier mobility
Squeezing is effective for high frequency operation.
It

By the above method, a silicon film in an amorphous state is formed to a thickness of 500 to 3000 Å, for example 1500 Å, and then heat treatment at a temperature of 450 to 700 ° C. for 12 to 70 hours at a medium temperature in a non-oxide atmosphere, For example, it was held at a temperature of 600 ° C. in a hydrogen atmosphere. Since the amorphous silicon oxide film is formed on the surface of the substrate below the silicon film, no specific nuclei are present in this heat treatment, and the whole is uniformly annealed.

The annealing causes the silicon film to shift from an amorphous structure to a highly ordered state, and a part of the silicon film exhibits a crystalline state, and the mobility of carriers that can be obtained is hole mobility (μh) = 1.
0-200 cm ² / VSec, electron mobility (μe) = 15
˜300 cm ² / VSec is obtained.

In FIG. 12 (A), the silicon film is photoetched using a first photomask, and a region 30 (channel width 20 μm) for PTFT is provided on the left side of the drawing, and NTF is used.
A region 40 for T was made on the right side.

A silicon oxide film was formed thereon as a gate insulating film 53 to a thickness of 500 to 2000Å, for example 700Å. This is the same condition as the production of the silicon oxide film 51 as the blocking layer. Add a small amount of fluorine during this film formation,
You may fix sodium ion. Further, in this embodiment, a silicon nitride film 54 of 50 to 200 Å, for example 100 Å, is formed on the silicon oxide film as a blocking layer having a function of suppressing the reaction between the gate electrode formed on the upper surface and the gate insulating film.

After that, as a material for the gate electrode, aluminum 30 is formed on the upper side by a known sputtering method.
The thickness is from 00Å to 1.5 μm, for example, 1 μm.

As the gate electrode material, in addition to aluminum, molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), an alloy obtained by mixing these materials with silicon, or a laminated wiring of silicon and a metal film is used. Etc. can be used.

When a metal material is used for the gate electrode as in the present embodiment, especially when a low resistance material such as aluminum is used, a gate delay (voltage propagating through the gate wiring) caused by a large area and high definition of the substrate is obtained. It is possible to suppress an increase in pulse delay and waveform distortion, and it is possible to easily increase the area of the substrate.

Further, an insulating film 4 is formed on the gate electrode material.
As a reference numeral 9, a silicon oxide film having a thickness of 3000 Å to 1 μm, here 6000 Å is formed by the sputtering method, and then the insulating film 49 and the gate electrode material are patterned by a second photomask to obtain a pattern shown in FIG. As described above, the gate electrode 55 for PTFT and the gate electrode 56 for NTFT were formed. All of these gate electrodes are connected to the same gate wiring 57.

Next, this substrate was mixed with 1% of a 3% tartaric acid aqueous solution and propylene glycol was added at a ratio of 9 to AG.
It was dipped in a W electrolytic solution, an aluminum gate electrode was connected to an anode of a power source, and platinum was used as a cathode to apply a DC power. At this time, the gate electrodes are connected to each gate wiring, but the connection terminals are provided so that all the gate wirings are sandwiched and connected near the edge of the substrate, and anodic oxidation is performed, as shown in FIG. 12C. Anodized films 58 and 59 were formed near the side surfaces of the gate electrode.

The anodizing condition is as follows. First, a current density of 4 mA / cm ² is applied for 20 minutes in a constant current mode, and then a constant voltage mode is applied for 15 minutes. Formed. It is better to form this anodic oxide film as thick as possible, and as thick as process conditions permit.

Next, as shown in FIG. 13A, after the nitride film 54 and the silicon oxide film 53 on the semiconductor are removed by etching, 1 to 1 of boron is added as an impurity for the PTFT to the entire surface of the substrate.
It was added by an ion implantation method at a dose amount of 5 × 10 ¹⁵ cm ⁻² . The source 60 and the drain 61 of the PTFT are formed with the doping concentration of about 10 ¹⁹ cm ^-3 . In this embodiment,
Ion doping was performed after removing the insulating film on the surface. However, if the conditions of ion implantation are changed, it is possible to dope through the insulating films 53 and 54 on the semiconductor film.

Next, as shown in FIG. 13B, a photoresist 61 is formed using a third photomask, and PTFT is formed.
After covering the area, the source 62 drain 63 for the NTFT
On the other hand, phosphorus was added by a dose amount of 1 to 5 × 10 ¹⁵ cm ^{-2 by} the ion implantation method so that the doping concentration was about 10 ²⁰ cm ^-3 . In the ion doping process as described above, the ion implantation direction is inclined with respect to the substrate, and the impurities are circulated in the direction below the anodic oxide film near the side surface of the gate electrode so that the ends of the source and drain regions are removed. The edges of the gate electrode were made to substantially coincide with each other. As a result, the anodic oxide film has a sufficient insulating action with respect to the electrode wiring formed in a later step, and it is not necessary to form a new insulating film.

Next, a heating anneal was performed again at 600 ° C. for 10 to 50 hours to activate the impurity regions. P
The source 60 and the drain 61 of the TFT, the source 62 and the drain 63 of the NTFT are prepared as P ⁺ and N ⁺ by activating impurities. Channel forming regions 64 and 65 are formed below the gate electrodes 55 and 56. In this embodiment, thermal activation is used as the activation treatment, but other than this method, a method of irradiating the source and drain regions with laser light to perform activation treatment can also be employed. In this case, since the activation process is performed instantaneously, it is not necessary to consider the diffusion of the metal material used for the gate electrode, and the function of blocking on the gate insulating film adopted in this embodiment is used. It is also possible to omit the silicon nitride film 54.

Next, an insulating film was formed on this upper surface as a silicon oxide film by the above-mentioned sputtering method. The thickness of this coating is as thick as possible, for example, 0.5 to 2.0 μm. In the present embodiment, it is formed to a thickness of 1.2 μm, and then anisotropic etching is performed from the top surface of the insulating film, the gate electrode and the anode. The residual region 6 is formed near the side wall of the convex portion formed of the oxide film.
6 is formed. This is shown in FIG. 13 (C).

Next, using the convex portion and the residual region 66 as a mask, unnecessary portions of the semiconductor film 52 are removed by etching to remove the residual region 66 existing near the side surface of the convex portion, and the convex portion is removed. The semiconductor film 52 to be the source and drain regions of each TFT was exposed to the outside. This state is shown in FIG.
It shows in (A).

Further, aluminum is formed on the whole by sputtering, and the leads 67, 68 and the contact portions 69, 70 are patterned by the fourth mask, and then the electrodes 67, 68, 69, 70 and the gate electrodes. The insulating film 49 on 55 and 56 and the semiconductor film which is in the vicinity of the side surfaces of the anodized films 58 and 59 are removed by etching, and complete element isolation is performed to complete the TFT. With such a manufacturing method, a TFT having a complementary structure could be manufactured with four masks. This situation is shown in Figure 1.
4 (B).

In this TFT, the periphery of the side of the gate electrode is wrapped with an anodic oxide film, and the source and drain regions protrude from the gate electrode portion only at the electrode connecting portion, but all other portions exist below the gate electrode. . Further, the source and drain electrodes are in contact with each other at the upper surface and the side surface of the source and drain regions, so that a sufficient ohmic connection is guaranteed.

By doing so, the C / TFT can be manufactured without applying a temperature above 700 ° C. in all steps, even though it is a self-aligning method. Therefore, it is not necessary to use an expensive substrate such as quartz as the substrate material, and the process is extremely suitable for the liquid crystal electro-optical device having a large pixel of the present invention.

In this embodiment, the thermal anneal is as shown in FIG.
It carried out twice in FIG. 13 (B). However, the anneal of FIG. 12 (A) may be omitted depending on the desired characteristics, and both may be combined with the anneal of FIG. 13 (B) to reduce the manufacturing time. Further, although aluminum is used as the gate electrode in the present embodiment, since the silicon nitride film 54 is provided under the aluminum,
Good interface characteristics could be realized without aluminum reacting with the underlying gate insulating film.

Next, as shown in FIG. 14C, two TFTs are provided.
In order to connect the output terminal of one of the pixels of the liquid crystal device with the transparent electrode as a transparent electrode, ITO (indium tin oxide film) was formed by sputtering. It was etched with a fifth photomask to form the pixel electrode 71. This ITO is room temperature to 1
The film was formed at 50 ° C., and was accomplished by oxygen at 200 to 400 ° C. or an anneal in the atmosphere. Thus PTFT
30, the NTFT 40, and the transparent conductive film electrode 71 were formed on the same glass substrate 50. The electric characteristics of the obtained TFT are PTFT, mobility is 20 (cm ² / Vs), and Vth is −
5.9 (V), NTFT has a mobility of 40 (cm ² / Vs),
Vth was 5.0 (V).

FIG. 15 shows the arrangement of electrodes and the like of this liquid crystal electro-optical device. The cross section taken along the line CC ′ of FIG. 15A corresponds to the cross section of the manufacturing process of FIGS. 12 to 14. PT
The FT 30 is provided at the intersection of the first signal line 72 and the third signal line 57, and the first signal line 72 and the third signal line 7 on the right side are provided.
Similarly, PTFTs for other pixels are provided at the intersections with 6 as well. On the other hand, the NTFT is provided at the intersection of the second signal line 75 and the third signal line 57. Further, a PTFT for another pixel is provided at the intersection of the other adjacent first signal line 74 and third signal line 57. A matrix structure using such C / TFT is provided. P
The TFT 30 has a drain 61 electrode and a first signal line 72.
And the gate 55 is connected to the signal line 57. The output end of the source 60 is connected to the pixel electrode 71 via a contact.

On the other hand, the NTFT 40 is connected to the second signal line 73 by the electrode of the source 62, and the gate 56 is connected to the signal line 57.
The output terminal of the drain 63 is connected to the PTF via the contact.
Like T, it is connected to the pixel electrode 71. In addition, another C connected to the same third signal line and provided next to it
As for / TFT, PTFT31 is connected to the first signal line 74 by NTFT
41 is connected to the second signal line 75. Thus, one pixel 80 is constituted by the pixel electrode 71 made of a transparent conductive film and the C / TFT between the pair of signal lines 72 and 73 (inside). By repeating such a structure horizontally and vertically, a 2 × 2 matrix can be made into a large pixel liquid crystal electro-optical device such as 640 × 480 or 1280 × 960. Note that the impurity regions of the TFT are called source and drain here for the purpose of explanation, and when actually driven, the function may be different from the name.

In this embodiment, the semiconductor film 52 is formed as the first film.
Using the photo mask of
The elements of each TFT are separated. Therefore, the semiconductor film does not exist under the gate wiring other than the TFT region, and the substrate under the gate wiring is the substrate or the insulating film on the substrate, and the capacitance on the gate input side is formed in this portion. Therefore, high-speed response is possible.

Further, FIG. 15B shows a sectional view corresponding to the DD ′ section in FIG. As described above, in the present invention, since the insulating film 49 is always provided on the gate electrode wiring at the intersection of the gate electrode wirings 57 and 76 and the wiring 72, it is possible to prevent the generation of capacitance due to the wiring in this portion.
It has become possible to manufacture an integrated circuit of a TFT having a multilayer wiring structure with only four masks.

A liquid crystal electro-optical device is manufactured by using the substrate provided with the active element thus manufactured. First, a resin in which 50% by weight of a nematic liquid crystal was dispersed in an epoxy modified acrylic resin having ultraviolet curing characteristics was formed on this substrate by a screen method. The screen used had a mesh density of 125 mesh per inch and an emulsion thickness of 15 μm. The squeegee pressure was 1.5 kg / cm ² .

Then, after leveling for 10 minutes, 236 nm.
With a high-pressure mercury lamp with an emission wavelength centered on
Applying energy of 000mJ to cure the resin, 12
A light control layer having a thickness of μm was formed.

Thereafter, the DC sputtering method is used to form Mo.
(Molybdenum) was formed into a 2500 Å film to form a second electrode.

Thereafter, a black epoxy resin is printed by using a screen method, and after calcination at 50 ° C. for 30 minutes,
Main baking was performed at 180 ° C. for 30 minutes to form a protective film of 50 μm.

A TAB-shaped drive IC was connected to the leads on the substrate to complete a reflective liquid crystal display device composed of only one substrate.

In this embodiment, one set of complementary TFTs is provided for each pixel as an active element, but the present invention is not limited to this structure, and a plurality of sets of complementary TFs are provided.
T may be provided, and a plurality of sets of complementary type TFTs
May be provided on the pixel electrode divided into a plurality of parts.

In this way, the liquid crystal electro-optical device in which the active element is provided in the dispersion type liquid crystal is completed. Since the dispersion type liquid crystal of the present embodiment requires only one substrate, a light and thin liquid crystal electro-optical device can be realized at a low cost, a deflecting plate is not used, and an alignment film is not required. Since the liquid crystal electro-optical effect can be realized with only the substrate, a very bright liquid crystal electro-optical device could be realized. The present invention can also be applied to one of the substrates of other liquid crystal electro-optical devices.

[Embodiment 2] In this embodiment, the present invention is applied to a liquid crystal electro-optical device in which a modified transfer gate TFT having a complementary structure is provided for one pixel as shown in FIG. The fabrication of the TFT in this embodiment is basically the same as that of the first embodiment, and the process is almost as shown in FIGS.
Proceed as in 4. However, since the modified transfer gate C / TFT is used in this embodiment, the structure shown in FIG.
2 to FIG. 14, the actual layout is different from that in FIG.
The TFTs are arranged and connected at the positions shown in FIG.

As shown in FIG. 16, the common gate wiring 9
The PTFT 95 and the NTFT 96 are connected to the gate 1 to connect the source and drain regions to the other signal line 93. The other source and drain regions are also commonly connected to the pixel electrode. There is.

First, the magnetron RF is placed on the glass 98.
(High frequency) A silicon oxide film as the blocking layer 99 is formed to a thickness of 1000 to 3000 Å by using a sputtering method. Process conditions are 100% oxygen atmosphere, film formation temperature 15
The output was 400 to 800 W and the pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 Å / min.

A silicon film 97 was formed thereon by LPCVD (Low Pressure Vapor Phase) method, sputtering method or plasma CVD method.

In FIG. 17A, a silicon film was photoetched with a first photomask to form a region for PTFT on the left side of the drawing and a region for NTFT on the right side. In the case of the present embodiment, unlike the case of the first embodiment, this semiconductor region is defined to be the region of the TFT. On the other hand, in the case of Example 1, since the area of the TFT is defined again by anisotropic etching in a later step, the first mask was roughly aligned.

A silicon oxide film is formed on the gate insulating film 103.
The thickness is 500 to 2000Å, for example, 700Å. This is the same condition as the production of the silicon oxide film 99 as the blocking layer.

After that, as a material for the gate electrode 107, an alloy of aluminum and silicon of 3000 Å to 1.5 μm, for example, 1 μ is formed on the upper side by a known sputtering method.
It was formed to a thickness of m.

As the gate electrode material, in addition to aluminum silicide, molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), chromium (Cr), alloys of these materials mixed with silicon, or these materials are used. An alloy of the material itself, a laminated wiring of silicon and a metal coating, or the like can be used.

Further, the insulating film 1 is formed on the gate electrode material.
17B, a silicon oxide film having a thickness of 3000 Å to 1 μm, here 6000 Å, is formed by a sputtering method, and the insulating film 106 and the gate electrode 107 are patterned by a second photomask. Thus, the gate electrode 107 and the insulating film 106 were formed.

Next, the substrate was mixed with 1% of a 3% tartaric acid aqueous solution and propylene glycol was added at a ratio of 9 to AG.
It was immersed in a W electrolytic solution, an aluminum silicide gate electrode was connected to an anode of a power source, and a direct current power was applied using platinum as a counter cathode. At this time, the gate electrode is connected to each gate wiring, but the connection terminals are provided so that all the gate wirings are sandwiched and connected in the vicinity of the end portion of the substrate, and anodic oxidation is performed, as shown in FIG. 17C. An anodic oxide film 100 was formed near the side surface of the gate electrode.

Next, as shown in FIG. 17D, after the insulating film 103 on the semiconductor is removed by etching, boron is added to the entire surface of the substrate as an impurity for PTFT with 1 to 5 × 10 ¹⁵ cm ^-2.
Was added by the ion implantation method. The doping concentration is set to about 10 ¹⁹ cm ^-3 to form the source and drain regions of the PTFT. In the present embodiment, ion doping was performed after removing the insulating film on the surface, but if the conditions of ion implantation are changed, it is possible to dope through the insulating film 103 on this semiconductor film.

Next, as shown in FIG. 18A, a photoresist 110 is formed using a third photomask, and PTF is used.
After covering the T region, source for NTFT - scan, with respect to the drain region, de of phosphorus 1~5 × 10 ¹⁵ cm ^-2 - added by an ion implantation method in amount's, doping concentration 10 ²⁰ cm ^{- It} was set to about ³ . In the ion doping process as described above, the ion implantation direction is inclined with respect to the substrate, and the impurities are circulated in a direction below the anodic oxide film near the side surface of the gate electrode so that the source / drain regions 104,
The end of 105 was made to substantially coincide with the end of the gate electrode. As a result, the anodic oxide film 100 has a sufficient insulating action with respect to the electrode wiring formed in a later step, and it is not necessary to form a new insulating film.

Next, the source and drain regions are irradiated with laser light for activation treatment. In this case, since the activation treatment is instantaneously performed, diffusion of the metal material used for the gate electrode is taken into consideration. Therefore, a highly reliable TFT could be manufactured.

Further, after aluminum is formed on the whole by sputtering and the electrode leads 102 are patterned by the fourth mask, the insulating film 106 on the electrodes 102 and the gate electrodes 107 and the anodic oxide film 100 near the side surfaces thereof are formed. The semiconductor film overhanging is removed by etching to complete element isolation to complete the TFT.
With such a manufacturing method, a TFT having a complementary structure could be manufactured with four masks. This state is shown in FIG.
It shows in (B).

Next, as shown in FIG. 18C, two TFTs are provided.
In order to connect the output terminal of one of the pixels of the liquid crystal device with the transparent electrode as a transparent electrode, ITO (indium tin oxide film) was formed by sputtering. It was etched with a fifth photomask to form the pixel electrode 108.

As described above, FIG.
A modified transfer gate TFT having the arrangement and structure shown in FIGS. FIG. 19B is a cross-sectional view corresponding to the FF ′ cross section of FIG.
FIG. 19C is a cross-sectional view corresponding to the EE ′ cross section of FIG. As is clear from FIGS. 19B and 19C, the interlayer insulating film 106 is always present on the gate electrode 107, and the lead portion, the source, and the drain of the gate wiring 107 as shown in FIG. A sufficient interlayer insulating function was exhibited at the intersection of the wiring 102 and the lead portion, and generation of wiring capacitance at this intersection could be suppressed.

As described above, in this embodiment, the first embodiment is used.
With the same number of masks as the above, without using a high-level process technology called anisotropic etching, there is less capacitance near the wiring, less possibility of short circuit near the gate insulating film, and active TFT with an element structure. The element substrate could be completed.

Using this substrate as a first substrate and a second substrate having a counter electrode and an alignment treatment layer formed on a counter substrate, STN type liquid crystal is injected between the substrates by a well-known bonding technique. As a result, an active matrix STN liquid crystal electro-optical device was completed.

Although all of the above examples are applied to the liquid crystal electro-optical device, the present invention is not limited to this example, and it is needless to say that the present invention can be applied to other devices and three-dimensional integrated circuit elements. Yes.

[0096]

According to the structure of the present invention, it becomes possible to manufacture a TFT element by using a very small number of masks as compared with the conventional one. When a semiconductor product is manufactured by applying an element of this structure, it is possible to simplify the manufacturing process and improve the manufacturing yield as the number of masks decreases.
As a result, it was possible to provide a semiconductor application device with a low manufacturing cost.

According to the present invention, a metal material is used as the gate electrode material, and an oxide film of this metal material by an anodic oxidation method is provided on the surface, and three-dimensional wiring having a three-dimensional intersection is provided thereon. Is characterized by. Further, the gate electrode and the oxide film near the side surface of the electrode are provided so that only the source / drain contact portions are exposed from the gate electrode to bring the feeding point closer to the channel, thereby lowering the frequency characteristics of the device and increasing the ON resistance. Could be prevented.

Further, in the present invention, when aluminum is used as the gate electrode material, hydrogen in the gate oxide film is reduced to H ₂ → H by the catalytic effect of aluminum during annealing in the element forming process, and further reduced. The interface state density (Q _SS ) can be reduced and the device characteristics can be improved as compared with the case where the silicon gate is used.

Further, since the source and drain regions of the TFT are self-aligned and the contact portions of the electrodes for supplying power to the source and drain regions are also defined as self-aligned lines, the area of the element required for the TFT is reduced and the integration degree is reduced. Can be improved. Moreover, when used as an active element of a liquid crystal electro-optical device, the aperture ratio of the liquid crystal panel could be increased.

Further, a TFT having a characteristic structure is proposed by positively utilizing the anodic oxide film near the side surface of the gate electrode.
In addition, the number of masks for manufacturing this TFT was at least two, and it was possible to manufacture with a very small number of masks.

[Brief description of drawings]

FIG. 1 shows an example of a device structure of a TFT of the present invention.

FIG. 2 shows a device structure of a conventional TFT.

FIG. 3 shows a schematic cross-sectional view of the manufacturing process of the TFT of the present invention.

FIG. 4 is a schematic cross-sectional view of the manufacturing process of the TFT of the present invention.

FIG. 5 shows a top view of the manufacturing process of the TFT of the present invention.

FIG. 6 shows a top view of the manufacturing process of the TFT of the present invention.

FIG. 7 is a schematic cross-sectional view of another manufacturing process of the TFT of the present invention.

FIG. 8 is a schematic cross-sectional view of another manufacturing process of the TFT of the present invention.

FIG. 9 shows a top view of another manufacturing process of the TFT of the present invention.

FIG. 10 shows a top view of another manufacturing process of the TFT of the present invention.

FIG. 11 shows a schematic diagram of a circuit when the TFT of the present invention is applied to a liquid crystal electrochemical device as a complementary type.

FIG. 12 is a schematic sectional view of a manufacturing process when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 13 is a schematic sectional view of a manufacturing process when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 14 is a schematic sectional view of a manufacturing process when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 15 is a schematic view showing a state of arrangement on a substrate when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 16 is a schematic diagram of a circuit when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 17 is a schematic sectional view of a manufacturing process when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 18 is a schematic sectional view of a manufacturing process when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

FIG. 19 is a schematic view showing a state of arrangement on a substrate when the TFT of the present invention is applied to a liquid crystal electro-optical device as a complementary type.

[Explanation of symbols] 1 substrate 2 semiconductor layers 3 Source and drain regions 6 Gate insulation film 7 Source and drain electrodes 8 gate electrodes 10 Anodized film 11 Insulating film 13 remaining area 49 insulating film 55 Gate electrode 56 gate electrode 60 sources 61 drain 62 Source 63 drain 66 Remaining area 71 Pixel electrode 100 Anodized film

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-2-307273 (JP, A) JP-A 63-250178 (JP, A) JP-A 1-149475 (JP, A) JP-A 58- 164268 (JP, A) JP 64-23575 (JP, A) JP 58-88784 (JP, A) JP 58-4180 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/336

Claims (4)

(57) [Claims] 1. An island-shaped semiconductor film is formed on an insulating substrate , a gate insulating film is formed on the island-shaped semiconductor film and the insulating substrate , and a gate electrode and a gate are formed on the gate insulating film. On the electrode
A first insulating film in contact is formed, and an anodic oxide film is formed on a side surface of the gate electrode. Among the gate insulating films, the gate electrode and the anodic oxide film are formed.
The film and the portion not covered with the first insulating film are etched.
Removed by etching to remove the gate electrode, the anodic oxide film, and the first insulating film.
Impurities are introduced into the island-shaped semiconductor film using the film as a mask.
To form the source and drain regions
And, said first insulating film, the anodic oxide film, and said etching
Each side of the gate insulating film partially removed by
Source and drain regions are formed while contacting the surface
So that the edges of the island-shaped semiconductor film thus exposed are exposed.
The island-shaped semiconductor having a drain region and a drain region formed therein.
A second insulating film is formed on the body film, and the gate electrode, the anodic oxide film, the first insulating film,
And using the second insulating film as a mask, the source region and
Exposing the island-shaped semiconductor film on which the drain region is formed
The second insulating layer after the removed portion is removed by etching.
By removing the film, the source region and the drain region are removed.
Region and the source region and the island-shaped semiconductor film
To expose the fine said drain region, said with contact with the upper surface of the exposed the source regions first
Forming an electrode extending to above the first insulating film, and a extending electrode to above the first insulating film with contact with an upper surface of the front <br/> Symbol drain region exposed A method of manufacturing a thin film transistor , comprising: Wherein a blocking layer is formed on an insulating substrate, the blocking island-shaped semiconductor film is formed on the layer, a gate insulating film formed in the island-shaped semiconductor film and the blocking layer, the On the gate insulating film, on the gate electrode and on the gate electrode
A first insulating film in contact is formed, and an anodic oxide film is formed on a side surface of the gate electrode. Among the gate insulating films, the gate electrode and the anodic oxide film are formed.
The film and the portion not covered with the first insulating film are etched.
Removed by etching to remove the gate electrode, the anodic oxide film, and the first insulating film.
Impurities are introduced into the island-shaped semiconductor film using the film as a mask.
To form the source and drain regions
And, said first insulating film, the anodic oxide film, and said etching
Each side of the gate insulating film partially removed by
Source and drain regions are formed while contacting the surface
So that the edges of the island-shaped semiconductor film thus exposed are exposed.
The island-shaped semiconductor having a drain region and a drain region formed therein.
A second insulating film is formed on the body film, and the gate electrode, the anodic oxide film, the first insulating film,
And using the second insulating film as a mask, the source region and
Exposing the island-shaped semiconductor film on which the drain region is formed
The second insulating layer after the removed portion is removed by etching.
The film of the island-shaped semiconductor film is removed by removing the film.
The source region and the drain region are exposed to contact the upper surface of the exposed source region and the first region .
Forming an electrode extending to above the first insulating film, and a extending electrode to above the first insulating film with contact with an upper surface of the front <br/> Symbol drain region exposed A method of manufacturing a thin film transistor , comprising: Wherein a blocking layer is formed on an insulating substrate, the blocking island-shaped semiconductor film is formed on the layer, a gate insulating film formed in the island-shaped semiconductor film and the blocking layer, the A silicon nitride film is formed on the gate insulating film, and the silicon nitride film is contacted with the gate electrode and the gate electrode.
A first insulating film is formed , an anodic oxide film is formed on a side surface of the gate electrode, and the gate electrode and the anodic oxide film among the gate insulating film are formed.
The film and the portion not covered with the first insulating film are etched.
Removed by etching to remove the gate electrode, the anodic oxide film, and the first insulating film.
Impurities are introduced into the island-shaped semiconductor film using the film as a mask.
To form the source and drain regions
And, said first insulating film, the anodic oxide film, and said etching
Each side of the gate insulating film partially removed by
Source and drain regions are formed while contacting the surface
So that the edges of the island-shaped semiconductor film thus exposed are exposed.
The island-shaped semiconductor having a drain region and a drain region formed therein.
A second insulating film is formed on the body film, and the gate electrode, the anodic oxide film, the first insulating film,
And using the second insulating film as a mask, the source region and
Exposing the island-shaped semiconductor film on which the drain region is formed
The second insulating layer after the removed portion is removed by etching.
The film of the island-shaped semiconductor film is removed by removing the film.
The source region and the drain region are exposed to contact the upper surface of the exposed source region and the first region .
Forming an electrode extending to above the first insulating film, and a extending electrode to above the first insulating film with contact with an upper surface of the front <br/> Symbol drain region exposed A method of manufacturing a thin film transistor , comprising: 4. The blocker according to claim 2 or 3.
The thin film transistor is characterized in that the insulating layer is made of silicon oxide.
How to make a transistor.